Taxonomy: Class Blastocystea
Animal: Blastocystis hominis (epidemiology) 8 19.jpg
Blastocystis hominis - proposed life cycle - Boreham & Stenzel. Blastocystis lives in the colon- there are different forms: 1. small avacuolar (or with very small vesicles) form, 5microns with 1 or 2 nuclei. It may transform into an 2. amoeboid form - these forms may be missed because of small size or because they degenerate after passage. The avacuolar form changes to a 3. multi-vacuolar form and then a 4. central vacuolar form and then a 5. granular form when cultured or passed from the colon (all 5-20 microns with 1-4 nuclei) - these used to be thought to be the 'typical' and only forms but they are not the forms in the colon. The avacuolar form also gives rise to the cyst form (5 microns) - this may be the transmissible stage. Cysts have one or more nuclei, a thick cyst wall and very small vacuoles (see Bibliography for reference details and other B. hominis slides).

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